What about Oz? With the exception of Beecher, all of the regular characters came from poor or working class backgrounds. Not just the prisoners either; I'd say that counts for the guards and administration as well, except maybe Warden Glynn.
Also, on Queer As Folk US, Debbie and Michael Novotny and Debbie's brother Vic Grassi were working class. Maybe Emmett too, although I think his situation was more that he didn't have the attention span to stick with one job for very long so he was constantly bouncing from one job to the next and short of funds.
Finally, I know you're not counting sci-fi/fantasy but nearly all of the characters in Jericho were small town working class. There were cops and doctors but the setting (and the premise) puts them at a different level than their counterparts on big city shows like CSI and Grey's Anatomy. Other characters were farmers and miners.